Fllotation process for concentration of pollucite ores



3,167,215 FLOTATION PROCES FOR CONCENTRATION OF PGLLUCITE ORES Karl C.Dean, Salt Lake City, Utah, assignor to the United States of America asrepresented by the Secretary of the Interior N Drawing. Filed Jan. 25,1962, Ser. Ne. 168,848 11 Claims. (61. 209-166) (Granted under Title 35,US. Code (1952), see. 266) The invention herein described and claimedmay be manufactured and used by or for the Government of the UnitedStates of America for governmental purposes without the payment ofroyalties thereon or therefor.

This invention relates to separation or concentration ofcesium-containing minerals from their ores in order to facilitaterecovery of cesium metal or cesium salts.

Cesium occurs chiefly as the mineral pollucite (C520 A1203 H2O GT 203202A1 O3 in ores which also contain a variety of other minerals such asmuscovite, albite, microline, quartz, lepidolite, oligoclase andspodutmene. These ores contain other alkali metals in addition to thecesium in the pollucite. The removal of cesium from its ores iscomplicated by the presence of the other alkali metals, particularlyrubidium, since the'problem of removing these elements from solutionsobtained from solubilizing pollucite ore is costly and difiicult.Present day refining techniques by direct metal reduction require one ormore distillations of the mixed alkali metals to obtain relatively purecesium. Preliminary separation of the cesium mineral from thosecontaining the other alkali metals would obviate the necessity for thesedistillations.

Other processes for recovering cesium involve production of cesiumsalts. Such processes require the use of expensive precipitants and ionexchange materials for separation of the cesium from other alkalimetals. Their use is reduced or eliminated by concentration of thecesium mineral from a cesium ore.

Accordingly, it is an object of the present invention to provide asimple and economical method for concentrating pollucite from its ore.

A further object of this invention is to provide a simple and economicalmethod of separation of pollucite from ores of relatively low pollucitecontent, thus enabling deposits of such ores to be brought intoproduction.

It is a further object of the present invention to provide a means forseparating cesium from other alkali metals present in cesium ores.

A further object of this invention is to provide a froth flotationmethod for the separation or concentration of pollucite from its ores.

A still further object of this invention is to provide a froth flotationprocess employing a particular combination of conditioning andcollecting agents in order to efiect a concentration of pollucite fromits ores.

Other objects and advantages will be apparent from the rest of thedisclosure.

It has now been found that pollucite may be effectively separated fromits ores by means of a froth flotation process in which a slurry of thepollucite ore is acidified, treated with a reagent such as hydrofluoricacid to depress the pollucite and then with a cationic reagent such asArmac CD (a coco amine acetate) which acts as a collector for themineral constituents of the ore other than the pollucite. The Arrmac CDalso has considerable frothing properties which eliminates the need fora further frother agent. The slurry is then aerated to form a froth inwhich the undesired minerals are collected in the froth and may beremoved, the desired pollucite remaining in the aqueous phase. Theprocess may be repeated if deite htates didiit sired to effect a stillfurther concentration of the pollucite.

The general procedure employed in the invention is a conventional frothflotation procedure in which the ore is first ground to fine particles,water is added to form a pulp and the pulp is passed to a flotation cellwhere reagents are added and air is introduced.

Selective floating of the individual minerals found in a complex orerequires the use of chemical compounds or reagents which either depressor collect specific mineral particles. Depression is achieved by addingreagents that make the mineral particle hydrophilic, or water loving.Collection is achieved by rendering mineral surfaces hydrophobic or airavid. Thus, with proper grinding and the use of satisfactory reagentssome of the mineral particles become air avid, attach themselves tobubbles, and float to the surface of the flotation cell and are removed.This particle product, or froth, is called a concentrate. Theconcentrate or froth product from a freshly ground and floated ore iscalled a rougher concentrate. The nonfloating or depressed mineralparticles from this initial separation remaining in the test cellcomprise the rougher tailing. In most laboratory flotation processes,some un desired mineral is mechanically entrapped in the froth productand this product is returned to the test cell (after removing therougher tailing), additional water added as required, and the productrefloated. The froth product of this reflotation is designated cleanerconcentrate No. 1, and the non-floated product, middling No. l, orsometimes cleaner tailing No. 1. The froth may be refloated, or cleanedseveral additional times, either with or without added reagents.Successive froth products would be called cleaner concentrates No. 2,No. 3, No. 4, etc. The nonfloated material in the successive steps wouldbe called either middling Nos. 1, 2, 3, 4, etc., or cleaner tailingsNos. 1, 2, 3, 4, etc. Some technologists use one term, some the other.Sometimes best results are obtained by floating the waste minerals awayfrom the valuable mineral. This type of procedure is employed in theinstant case and the waste minerals are collected as the concent-rate inthe froth while the pollucite remains in the cell and is designatedtailing even though it is actually a concentrate of the desired mineral.This conventional terminology has been employed in the discussion andexamples which appear below.

In laboratory flotation all of the concentrate to be removed may beaccomplished by the addition of all the reagents at one time,conditioning by agitation of the flotation pulp and reagents, adding airto the cell and floating the concentrate. This same objective, butusually with more selective separations, may be accomplished by partialadditions of the total reagents, conditioning, and flotation in stages,rather than all at one time. These staged reagent additions,conditioning periods, and concentrate floatings are continued untilinspections, or knowledge gained from previous tests, indicatesuflicient material has been floated.

The process is carried out at room temperature and pressure. The rawmaterial employed is a pollucite ore containing numerous minerals otherthan pollucite as described above. The exact composition of such oreswill of course vary according to the deposit from which the ore isobtained. The ore is first ground (wet or dry) to a degree of finenesssuflicient to liberate the cesium-bearing mineral, which may be fromless than about 48 mesh to less than about mesh. The ore is then floatedin its entirety or it may be first separated into two or more sizedfractions. Whether flotation of the entire ore or of aseparate sizedfraction is employed does not appear to materially affect the resultsand for economic reasons entire ore flotation is preferred. Theflotation is then effected by adding water in amounts sufficient tofurnish a pulp of between 20 and 45 percent solids. Sulfuric acid D isthen added to adjust the pH to a value of from 1.4 to 2.7. Hydrofluoricacid is then added in an amount sufficient to aid in the selectiveseparation of the pollucite. Though applicant does not wish to be boundby any theory as to the action of the hydrofluoric acid, it is believedthat its action is that of a depressant for the pollucite. Aluminumsulfate may also be added in small quantities for control of the frothif the ore is finely ground. The slurry is then conditioned by agitationfor about 10 minutes.

7 Following the conditioning step, a cationic reagent such as Armac CDis added and a further conditioning period of about 3 minutes isallowed. The slurry is then aerated to form a froth and float thenon-pollucite minerals which are then removed with the froth. Thepollucite mineral remains in the aqueous phase and may be recovered byfiltration. The concentrate containing the waste minerais may be againtreated as above to further concentrate the pollucite in the aqueousphase.

The sulfuric acid is usually added as a 10 percent by weight aqueoussolution but may be used in any concentration to provide the proper pH.About 10 to 20 pounds of the 10 percent acid per ton of ore is usuallyrequired in the initial stage to provide the proper pH. Successivestages will usually require 1 to pounds to maintain the proper pH. Thehydrofluoric acid is usually added as a 2.5 to 5 percent by weightaqueous solution and the total amount employed may vary from about 3.0to 12 pounds per ton of ore. Staged additions of the hydrofluoric acidmay range from about 1 to 4 pounds per ton of ore. The aluminum sulfateis usually added in the form of a percent by Weight aqueous solution.The total amount of aluminum sulfate is usually about 0.25 to 3 poundsper ton of ore, though staged additions may amount to 1 pound or lessper ton of ore. The Armac CD is usually added as a 5 percent by weightaqueous solution in amounts ranging from about 0.2 to 1.5 pounds per tonof ore for each stage or a total of between 0.6 and 4.5 pounds per tonof ore for the complete roughing cycle. The amounts of reagents employedin the cleaning stages in pounds per ton of ore are as follows: Sulfuricacid- 2.0 to 5.0, aluminum sulfate-none, hydrofluoric acid 1.0 to 4.0,and Armac CDzero to 0.5. These figures would be multiplied by the totalnumber of cleaning stages to get the total quantity of reagents for thecleaning phase. Actual concentrations of active ingredients in theaqueous reagent solutions may vary to a great extent, as from 1 to 48percent by weight, for all reagents except the collector reagent ArmacCD. The concentrations of cationic collectors such as Armac CD normallyare held at between 1 and 5 percent by weight to remain within thesolubility limits of the reagent and to allow better control of reagentadditions. The pH range is maintained between the values of 1.4 to 2.7to gain best over-all results. If the pH is much below the 1.4 valueadditional collector is required with no great increase in cesiumcontent of tailing. If the pH is much above the 2.7 value the cesiumcontent in the waste concentrate will be greater, thus loweringrecovery.

The Armac CD is a coco amine acetate manufactured by Armour & C0. Theamine portion of the Armac CD is composed of about 97 percent primaryaliphatic amines of 8 to 18 carbon atoms having a mean molecular weightof 200, a molecular combining weight of 206 and an approximate meltingpoint of 21 C. The percent composition of the primary amine content ofthe Armac CD is as follows: octyl, 8; decyl, 9; dodecyl, 47; tetradecyl,18; hexadecyl, 8; octadecyl, 5; and octadecenyl, 5.

The following examples will serve to more particularly describe theinvention.

EXAMPLE I apatite, 2; and tale, 1 was wet ground in an iron ball mill at66 percent solids for five 7-minute stages to give a product 98 percentminus-IOO-mesh. An additional 1500 milliliters of Salt Lake City tapwater was added to form a slurry of 33 percent solids. This slurry wasthen treated according to the following procedure using the proportionsof ingredients given in table 1 (rougher concentrate No. l). Sulfuricacid was added to give a pH of 2.6. The hydrofluoric acid and aluminumsulfate were then added and the mixture was conditioned for a period of10 minutes. The Armac CD was then added, followed by an additional 3minutes conditioning period. The mixture was then aerated to form afroth causing flotation of a first rougher concentrate. Three suchrougher concentrates were prepared using the reaction conditions givenin Table 1. The three rougher concentrates were then removed andcombined and subsequently cleaned in three stages. Each stage of thecleaning procedure consisted of return of the concentrate to the cellafter the tailing had been removed. The conditions employed in eachstage of the cleaning procedure are also given in Table l. The resultsof an analysis of the products of the separation are given in Table 1A.The head assay in Table 1A is simply an assay of the raw ore prior totreatment. The calculated head is derived from the weight and chemicalanalyses of the various products (concentrates and cleaner and roughertail) to serve as a comparison with the original analyses of the head.The calculated head furnishes a check as to the accuracy of weights andassays of the test products.

The effectiveness of applicants process may be seen from the increase ofthe cesium to rubidium ratio of 53 to l in the calculated head to 324 to1 in the final pollucite product comprising the combined cleaner androugher tailings.

Table 1 FLOTATION, CONDITIONING, AND REAGENT SCHEDULE RougherConcentrate Time, min. Reagent, lb./ton of ore Stage No. pH

Condi- Flo- H1304 HF A12(SO-l)3'18H2O Armac tioning tation CD CleanerConcentrate Essentially the same procedure was used in this secondexample as in Example I, but a different ore was used, the quantities ofreagents were changed, and the grind was varied. The ore represented inthis example was a Southern Rhodesian pollucite ore containing thefollowing minerals with percentages given-pollucite, 65; albite, 16;lepidolite, 13; quartz, 4; petalitc, 1; and spodumene, 1. The ore wasground in an iron ball mill for 20 minutes to give 98.7 percent of theore minus-100-mesh in size. Flotation of this ore increased thecesium-to-rubidium ratio from 32:1 to 83:1. The fact that some of therubidium was chemically combined with the pollucite prevented furtherseparation by physical concentration such as flotation. The testconditions and results are shown in Tables 2 and 2A.

Table 2 FLO'IATION, CONDITIONING, AND REAGENT SCHEDULE RougherConcentrate Time, min. Reagent, lb./ton of ore Stage No. pH

Condi- Flota, H150 HF Armac tioning tion CD 13 4 2. 6 12. 2. 0 0. 60 104 2. 3 4. O 1. O (i0 10 3 2. 3 3. 0 1. 0 30 Cleaner Concentrate 'Table2A RESULTS OF FLOTATION Assay, Distribution, Weight, percent percentProducts percent Cs Rb Cs Rb Combined cleaner concentrates NOS. 1, 2 25.6 7.03 1. 84 7. 5 63. 5 Combined cleaner and rougher taiL 74. 4 29.80 3692. 5 36. 5

Calculated head 100. 0 24. 00 74 100. 0 100. 0

EXAMPLE III This example is submitted for a Canadian pollucite ore toshow that the flotation method devised is applicable to pollucite oresof greatly difierent mineral assemblages. The Canadian ore had thefollowing percentages of mineral constituentspollcuite, 80; quartz, 7;microline, 5; albitecoligoclase, 3; spodumene, 3; amblygonite, 1; andmuscovite, 1. Chemical analysis and a mineralogical examination of theflotation products jointly indicated that much of the rubidium Wascombined chemically with the pollucite. The cesium-to-rubidium ratio wasnot changed radically by flotation, but this test does show that quartz,microcline, and spodumene may be separated from pollucite by thisinvention. Conditions and results are given in Tables 3 and 3A.

Hydrochloric or phosphoric acids may be used in place of sulfuric acidfor pH regulation; however, cost will normally rule out the possibilityof substituting these acids.

Various cationic collectors may be used in place of the Armac CD. Thesecationic reagents may be, for example, fatty amines, fatty amineacetates or quaternary ammonium salts. These reagents are sold under thefollowing trade names: Armeens, Armacs, Arquads and Ethomeens, all fromArmour Chemical Division as well as numerous other trade names forsimilar materials from other manufacturers.

The conditioning time, during which the reagents and pulp are intimatelymixed, may also be varied to obtain optimum results. The acidconditioning period is usually about ten minutes but may range fromabout 4 to 10 minutes. The second or collector conditioning time isusually about 3 rninutes. The values of conditioning time given in thetables is the total conditioning time in which a 3 minute period wasemployed for the collector conditioning.

Ambient temperature and pressure are usually satisfactory. Littledifliculty with temperature change should be expected if normal seasonalfluctuations are the extremes.

Ordinary city tap water containing an average of 66, 15 and 300 permillion of calcium, magnesium and total dry solids, respectively, wasused in all the tests. No difficulties should be encountered with mostavailable culinary waters though, of course, distilled or deionizedwater could also be used. Water is generally used in forming the pulpsince other liquids such as organic liquids are usually eliminated fromconsideration because of cost and interaction with the flotationreagents.

The laboratory flotation cells used in these tests were of the Galigherand Fagergren types. The Galigher type consists of a container with acentrally located impeller for inducing agitation within the pulp. Thiscell does not aerate the pulp by mechanical action but is supplied withlow pressure air, controlled by the flotation experimenter, from asuitable compressor. The Fagergren cell also has a centrally locatedimpeller for agitation which is enclosed by a standpipe containing avalve for air control. Air is drawn through the standpipe when needed byaction of the swiftly moving impeller. The air valve is closed duringperiods of agitation conditioning and opened to admit air when flotationis desired.

The process as described is a discontinuous process as all laboratorybatch cell type operations must be. However, the methods developed byusing laboratory cells are, if properly conducted, fully convertible touse in continuous many celled operations. In continuous operation theconcentrate would be removed from successive flotation cells withconditioning cells used between flotation cells to obtain proper contactbetween the reagents and the mineral particles by agitationconditioning.

Recovery of the concentrate is effected by collecting it in pans as itis scraped from the flotation cell and subsequently filtered. After allthe concentrates are floated the product remaining in the cell also isfiltered to remove the bulk of the water. The concentrates and tailingsmay be dried after filtration if such a product is desired. Incontinuous operation the concentrates and tailings are 7 discharged intoseparate launders (troughs) which discharge into thickeners. Thethickened products then are fed into filters where the majority of theWater is removed. Drying may follow if desired.

It will be appreciated from a study of the foregoing specifications thatthe invention described herein is capable of various modifications andchanges without departing firom its essential spirit and scope.

What is claimed is:

1. A process for the concentration of a cesium mineral from an orecontaining the same together with undesired minerals which comprises:adding to an aqueous pulp of said ore in a flotation cell (1) an acid inamount suflicient to adjust the pH to about 1.4 to 2.7; (2) a depressantfor the cesium mineral comprising hydrofluoric acid; (3) a collector forthe undesired minerals comprising a cationic reagent and then frothfloating the undesired minerals from the cesium mineral.

2. The process of claim 1 in which aluminum sulfate is also added to thepulp in order to control the froth.

3. The process of claim 1 in which the cesium mineral is pollucite.

4. The process of claim 1 in which the acid is sulfuric acid.

5. The process of claim 1 in which the cationic reagent is a coco amineacetate.

6. A process for the concentration of a cesium mineral from an orecontaining the same together with undesired minerals which comprises:adding to an aqueous pulp of said ore (1) an acid in an amountsufficient to adjust the pH to a value from about 1.4 to 2.7 and (2) adepressant for the cesium mineral comprising hydrofluoric acid, conclesof undesired mineral and then froth floating the undesired minerals fromthe cesium mineral.

7. The process of claim 6 in which the initial conditioning period is 10minutes and the second conditioning period is 3 minutes.

8. The process of claim 6 in which the depressant is added in an amountof from 3.0 to 12.0 pounds per ton of ore.

9. The process of claim 6 in which the collecting agent is added in anamount of from 0.6 to 4.5 pounds per'ton of ore.

10. A process for the concentration of acesium mineral from an orecontaining the same together with undesired minerals which comprises:adding to an aqueous pulp of said ore in a flotation cell (1) an acid inan amount sufficient to adjust the pH to a value of about 1.4 to 2.7;(2) a depressant for the cesium mineral comprising hydrofluoric acid;and (3) a collector for the undesired minerals comprising a cationicreagent, aerating the pulp in order to froth float a concentratecontaining the undesired minerals and leave the cesium mineral as thetailing in the aqueous phase and separating the concentrate and tailingfrom the cell.

11. The process of claim 10 in which the concentrate containing theundesired minerals and entrapped cesium mineral is returned to theflotation cell and refloated in order to further remove the cesiummineral from the undesired minerals in the concentrate.

References Cited in the file of this patent t UNITED STATES PATENTSOMeara Oct. 6, 1942 Browning et a1 Apr. 3, 1962 OTHER REFERENCESTaggart: (Handbook of Mineral Dressing), March 1956 (sec. 12-26).

1. A PROCESS FOR THE CONCENTRATION OF A CESIUM MINERAL FROM AN ORECONTAINING THE SAME TOGETHER WITH UNDESIRED MINERALS WHICH COMPRISES:ADDING TO AN AQUEOUS PULP OF SAID ORE IN A FLOTATION CELL (1) AN ACID INAMOUNT SUFFICIENT TO ADJUST THE PH TO ABOUT 1.4 TO 2.7; (2) A DEPRESSANTFOR THE CESIUM MINERAL COMPRISING HYDROFLUORIC ACID; (3) A COLLECTOR FORTHE UNDESIRED MINERALS COMPRISING A CATIONIC REAGENT AND THEN FROTHFLOATING THE UNDESIRED MINERALS FROM THE CESIUM MINERAL.